Set out three shallow bowls and a piece of parchment paper.
In the first bowl, add flour, salt and garlic powder.
In the second bowl, add eggs and whisk vigorously.
In the third bowl, add breadcrumbs.
Working one at a time, first, dip the mozzarella stick into the flour mixture, turning to coat all sides. Next, roll it into the eggs, coating all sides. Third, dip the mozzarella stick into the breadcrumbs. Finally, go back and dip the cheese stick in both the eggs and the breadcrumbs. The mozzarella stick should be fully coated. Place it onto the parchment paper.
Repeat with the remaining mozzarella sticks.
Place the coated cheese sticks into the freezer for at least 30 minutes, up to an hour.
When ready, preheat the air fryer to 390°F for 5 minutes.
Lightly spray the mozzarella sticks with cooking spray and carefully place them into the basket of the air fryer, leaving some space in between each cheese stick. (Depending on the size of your air fryer, you may have to work in batches.)
Air fry for 4-6 minutes, or until golden brown.
Remove from the air fryer and let cool for 1-2 minutes. Serve hot with marinara sauce.